The fluorescence excitation-emission matrix of Chromophoric dissolved organic matter (CDOM) samples from rainwater collected at Rameswaram, Tamilnadu, India are analysed. Total five peaks were observed for humic/marine and protein likes substances respectively. The peak A and C intensities varies form 1.98 ± 0.28 and 0.97 ± 0.11 QSU respectively represents humic like substances. The peak B and T intensities varies from 3.94 ± 0.75 and 7.42 ± 1.43 QSU showed association of protein like substances whereas peak M intensities varies from 1.92 ± 0.37 QSU indicates marine contribution. Among the fluorophores, the following sequence were observed as T > B > A > M > C which indicates dominance of Tryptophan like substances in rainwater. The average peak T/C ratios was observed as 7.88 ± 2.2 indicates microbial contamination by Tryptophan-like substances with the high biological activity and low volatility.

The present study investigated the chemical composition of precipitation at Comba, Madgaon, South Goa during southwest monsoon. The rainwater samples were collected on event basis during June-September 2008 and were analyzed for pH, major anions F, Cl, NO(3), SO(4)) and cations (Ca, Mg, Na, K, NH(4)). The pH value varied from 5.36 to 6.91 (6.25 +/- 0.28) indicating alkaline nature of rainwater and dominance of Cl and Na in precipitation. The Neutralization factors (NF) was found to be NFCa = 1.22, NFMg = 0.42, NFNH(4) = 0.37 and NFK = 0.14 indicating below cloud process in which crustal components are responsible for neutralization of anions.

Studies on precipitation chemistry were carried out to understand the nature and sources of rainwater at Rameswaram and NTPC Dadri, India representing coastal and industrial region during 2010. The rainwater samples, collected at these locations, were analyzed for major ions and pH. The data were assessed for its quality. The pH of rainwater at two locations varied from 5.53 to 6.73 and 5.1-6.6, indicating alkaline nature except a few acidic events. The dominance of Cl− and Na+ were observed in coastal environment whereas dominance of Ca2+ was seen in industrial environment. The nss-SO42-(37.9%) at Rameswaram is less influenced by anthropogenic activities whereas nss-SO42-(72.5%) at NTPC Dadri is influenced by pollutants emitted by anthropogenic sources. The ratio of H+/ (NO3-+ SO42-) was observed as 0.04 and 0.008 for Rameswaram and NTPC Dadri which is close to zero, indicate 99.99% of acidity was neutralized in precipitation. Ca2+, NH4+ and Mg2+ play an important role in neutralization of acidic ions in rainwater. For source identification, correlation matrix analysis was established, which showed that in general, at both sites; correlation between the acidic ions SO42-and NO3-indicating their origin from similar sources, because of the similarity in their behavior in precipitation and the coemissions of their precursors SO2 and NOX. The correlation coefficient of (SO42-+ NO3-) vs (Ca2+) at Rameswaram and NTPC Dadri were 0.77 and 0.87 indicates that CaCO3 is the major neutralizing agent for both the region. Overall, the influence of marine, terrestrial and anthropogenic sources was observed in the rain events.

The chemical composition of rainwater changes from place to place and region to region under the influence of several major factors, viz., topography, its distance from sea and overall rainfall pattern. The present study investigated the chemical composition of precipitation at Akkalkuwa, district Nandurbar, in the State Maharashtra during southwest monsoon. The rainwater samples were collected on event basis during June-September 2008 and were analyzed for pH, major anions (F, Cl, NO3, SO4) and cations (Ca, Mg, Na, K, NH4). The pH varied from 6.0 and 6.8 with an average of 6.29 ± 0.23 indicating alkaline nature and dominance of Ca in precipitation. The relative magnitude of major ions in precipitation follows the pattern as Ca>Cl>Na>SO4>NO3>HCO3>NH4>Mg>K>F>H. The Neutralization factor (NF) was found to be NFCa = 0.95, NFNH4 = 0.31, NFMg = 0.27 and NFK = 0.08 indicating below cloud process in which crustal components are responsible for neutralization of anions. Significant correlation of NH4 with SO4 and NO3 was observed with correlation coefficient of r = 0.79 and 0.75, respectively.